The republican terror group Oglaigh Na hEireann has claimed that a car bomb abandoned in County Fermanagh at the weekend was to be detonated at the hotel hosting the G8 summit of world leaders in June.

In a coded statement to the Guardian on Monday afternoon, the anti-ceasefire republican dissident organisation also admitted responsibility for an attempted mortar bomb attack on the heavily fortified New Barnsley police station in west Belfast two weeks ago.

By specifically referring to the hotel where Barack Obama, David Cameron, Vladimir Putin, François Hollande and the other leaders of the world's most powerful nations are staying, ONH has raised the security stakes before the G8 meeting on 17 June.

The five-star Lough Erne complex in Enniskillen, opened in 2007, is located on a 600-acre peninsula between Castle Hume Lough and Lower Lough Erne. Security was already expected to be tight for the visit of presidents and prime ministers to Fermanagh.

The Police Service of Northern Ireland (PSNI) has recently acquired a number of spy drones to be flown over the luxury hotel site during the talks in June while hundreds of police officers and security officials will be deployed into the border region for the biggest gathering of world leaders to visit Northern Ireland in its history.

On Saturday morning army bomb disposal officers defused a 60kg explosive device packed into a beer keg which had been left inside a car abandoned on the Derrylin Road near Enniskillen. Security sources initially thought that the target of the aborted bomb attack was the nearby Lisnaskea Police Service of Northern Ireland (PSNI) station which is one of the most heavily fortified police bases in Europe.

In response, however, ONH, which exists independently from the other main republican dissident paramilitary organisation calling itself the new IRA, claimed in Monday's statement that the Lough Erne hotel complex was the target.

Both ONH and the new IRA have been attempting to intensify their attacks on the security forces, mainly the PSNI, and other strategic targets in recent weeks. Earlier this month two men were arrested after police intercepted a van carrying four mortar bombs which were primed and ready to fire at a police station in Derry city. In the same month a mortar device similar to the one in the photograph sent to the Guardian was found close to New Barnsley police station on the loyalist side of the sectarian dividing line in west Belfast.

Another ONH terror attack this month using a booby trap bomb that was to be triggered by a mobile phone signal was designed both to kill police officers searching Belfast's Lough Shore area and synchronise with a mini Anglo-Irish summit between Cameron and the Irish premier, Enda Kenny, in Downing Street earlier this month.